1. Field of the Invention
The present invention relates to an image forming apparatus using electrophotographic technologies, such as a copying machine and a printer. More particularly, the invention relates to an image forming apparatus provided with a cartridge having a developer container in it, which is detachably mountable on such apparatus.
2. Related Background Art
Conventionally, for a cartridge type electrophotographic image forming apparatus, there has been adopted a process cartridge method or the like, which makes it possible to detachably mount a cartridge on the main body of an electrophotographic image forming apparatus by arranging the cartridge to be formed integrally with an electrophotographic photosensitive element and processing means. In accordance with a process cartridge method of this kind, it is possible for the user to maintain the apparatus by himself without any help from a serviceman. Therefore, its operativity has been enhanced significantly. The process cartridge method is now widely adopted for electrophotographic image forming apparatuses. Also, in consideration of the cartridge replacement to be made by the user himself for the maintenance of the apparatus as described above, warning means is provided to indicate on a display an amount of toner that has become small by detecting the residual toner amount in the development device, thus prompting the user to replace cartridges before the image density is lowered or some other defects may take place.
Also, there has been proposed a method whereby to count and store the frequency of use of a cartridge by the utilization of an EEPROM or other non-volatile memory means. For example, in accordance with Japanese Patent Laid-Open Application No. 61-185761, a description has been made of an electrophotographic image forming apparatus, which is provided with means for counting and storing information regarding toner reminders on the basis of information on the period of exposure each time images are recorded by means of laser beam, light emitting diode, or the like, on the photosensitive drum in a process cartridge.
Also, a cartridge of this kind is often mounted on or demounted from the main body of an apparatus. With this in view, a proposal has been made to enhance the accuracy of detection by providing memory means in the cartridge itself when a plurality of cartridges are used for one main body of the apparatus. For example, in accordance with Japanese Patent Laid-Open Application No. 63-212956, an electrophotographic image forming apparatus is proposed, wherein memory means is arranged in a cartridge, while it is arranged to provide the main body of the apparatus with means for reading from the memory and writing to it, and means for computing information related to the life of the cartridge on the basis of the contents read out from such memory means and the electrophotographic operations that have been carried out, and then, writing such information to the memory.
Also, as another method for detecting the consumption of toner, there has been proposed a method whereby to directly detect residual toner amount in a cartridge. For example, in accordance with Japanese Patent Laid-Open Application No. 62-62352, description is made of a method whereby to arrange a detection antenna in the vicinity of a development sleeve, which serves as a developer carrier, and measure each current induced to the antenna when an AC voltage is applied to the development sleeve, and then, to execute the toner detection by the utilization of the status changes of such current that may take place between the sleeve and the antenna depending on the residual toner amounts.
It is an object of the present invention to provide an image forming apparatus and a cartridge, which are capable of obtaining the residual amount of developer more accurately than the apparatuses that have been proposed conventionally.
It is another object of the invention to provide an image forming apparatus and a cartridge, which are capable of making the residual developer amount smaller.
It is still another object of the invention to provide an image forming apparatus and a cartridge, which are capable of informing the user of the life of the cartridge accurately.
It is a further object of the invention to provide an image forming apparatus and a cartridge, which are capable of informing the user of the life of the cartridge and the amount of residual developer in it accurately even if a used cartridge is mounted on the apparatus.
It is still a further object of the invention to provide an image forming apparatus comprising:
a cartridge, which is provided with a developer container, means for detecting its residual amount to detect the developer still remaining in the container, and memory means to store rewritable data on it;
access means to access data on the memory means, which writes on the memory the data on the number of printing sheets after the detected amount of the residual amount detection means arrives at a predetermined value; and
indication means to indicate the absence of developer when the data on the number of printing sheets on the memory arrives at the predetermined value.
Other objectives, features, and advantages of the invention will be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to accompanying drawings, which form a part thereof, and which illustrate an example of the invention. Such example, however, is not exhaustive of the various embodiments of the invention, and therefore reference is made to the claims which follow the description for determining the scope of the invention.